Project 2 - Biology of the cation-chloride-cotransporter, thick ascending limb of Henle’s loop

Project Summary

The straight part of the distal tubule plays a key role in renal salt- and water regulation by means of the function of its principal ion transporter, the Na+,K+,2Cl--cotransporter (NKCC2). Absence of NKCC2 in genetically engineered mice is not compatible with survival. Decreased function of NKCC2 results in early childhood hyperprostaglandin E-syndrome with severe impairments in systemic and renal volume and electrolyte homeostasis. Little data is currently available on the cell biology and regulation of NKCC2. Cellular determinants of NKCC2 function will therefore be studied in cell culture and in vivo models (rat, mouse). Conditions of non-genomic vs. genomic activation will have to be defined. We will test the hypothesis that an insertion of NKCC2 into cholesterol-rich membrane microdomains (rafts) is functionally relevant for its sorting and activation events. The role of lipid rafts will be tested experimentally. We will further study whether proteins that co-localize with NKCC2 in rafts can be detected, and whether these have an impact on NKCC2 function. We will also study proteins that interact with NKCC2 irrespective of raft association; their functional role will be tested. We are expecting new access to NKCC2 function in salt and volume regulation, and we hope to gain deeper insights into pathophysiological conditions determined by NKCC2 malfunction.

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